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  1. Leverage browser caching
  2. Parallelize downloads across hostnames
  3. Enable compression
  4. Combine images into CSS sprites
  5. Minify CSS

The first three are server-side changes, the latter-two can be done by Web Services.
See Webserver config change requests.

For the minification and concatenation of CSS and JS we could look at as tool to get us started.

Google's online Page Speed tool gives these results

Page Speed results April 1 2011


High priority. These suggestions represent the largest potential performance wins for the least development effort. You should address this item first:

  • Leverage browser caching

Medium priority. These suggestions may represent smaller wins or much more work to implement. You should address these items next:

  • Combine images into CSS sprites,
  • Optimize images

Low priority. These suggestions represent the smallest wins. You should only be concerned with these items after you've handled the higher-priority ones:

  • Inline Small JavaScript,
  • Defer parsing of JavaScript,
  • Minify CSS,
  • Minify HTML,
  • Minify JavaScript,
  • Specify a Vary: Accept-Encoding header

Additionally there are other standard practices we should be following:

  1. load JavaScript at the bottom of the page rather than the top
  2. optimize images
  3. Late loading of resources where not immediately necessary (images/HTML that are off-screen or accessible via JS, images/JS/HTML loaded later in the document where not immediately needed) - for example, work from China page loading time can be seen here - click on Agent Location.
  4. Reduce the number of requests where possible (CSS sprites, concatenate CSS and JS)

Other notes

Phil also suggest creating a JSP that works out what Javascript/CSS to include from the various ones specified for a page. This would reduce the number of requests massively. Many of the resources are specified as a page property, and we already know what the template would use.

Liam has also pointed out images may not be correctly compressed and looking at it indicates a saving of 309.8 KB.

We have not yet looked at optimising our HTTPS serving. There is a resource here which appears useful.


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